1. Field of the Invention
This invention relates generally to systems for locating an object and, more particularly, to systems for determining the position of a gaming ball relative to a playing field by use of radio frequency and ultrasonic transmitters and receivers.
2. Discussion of the Related Art
In certain games incorporating gaming balls, it is generally crucial to the fairness of the game that the location of the gaming ball be reasonably accurately determined relative to a playing field. Typically, multiple gaming officials are utilized for determining the ball's location, and thus, a certain amount of subjectivity is interjected into the game which may result in substantial mistakes due to human nature possibly affecting the fairness of the play. With particular reference to football, it is necessary to determine the location of the football so as to enable the officials to accurately monitor "first down" situations, as well as, repositioning the football relative to a previous location. Additionally, the speed at which the game is played may be substantially affected by how quickly the gaming ball can be accurately located. Furthermore, the number of gaming officials necessary to officiate the game may also be substantially dependent on the ability of the officials to accurately determine the ball location. Therefore, different methods have been employed to at least assist the gaming officials in determining the location of the gaming ball.
Current technology has seen the use of instant-replay video equipment utilized for immediate reevaluation of close game play. This method, however, requires the interaction between gaming officials and broadcast technicians and involves the use of expensive cameras and video equipment not normally available at most sporting events. Additionally, stop-action photography equipment has been used to record photo-finish events. This method, while providing a permanent record, introduces additional time delay into the particular sporting event unless used in conjunction with instant replay video equipment, and therefore, would be subject to the same disadvantages as mentioned above. Further, photosensitive devices have been installed at appropriate locations which are triggered when a gaming ball or other apparatus or player crosses marked boundaries. This method is, however, restricted to boundary locations and does not address the game ball's location during the vast majority of play when the ball is at random locations and not at or crossing a boundary. Also, buried wires have been placed on field boundaries to magnetically detect a modified game ball as it passes over marked boundaries. This method, similar to the photosensitive devices described above, also requires modification of the gaming ball or other apparatus restricting the use of commonly available sporting devices and subjecting the devices to the rigors of the game.
The use of ultrasonic devices to measure distances is known. Ultrasonic measurement is, however, generally dependent upon consistent transducer coupling to the surrounding environment and the relative stability of that environment. Inconsistent results occur because ultrasonic waves will change under different environmental conditions as the sound waves pass through various media. Furthermore, playing field conditions could dynamically change over the playing season as a result of climatic variances, and even change during a single game itself due to player activity or changes in weather. Because playing field conditions can vary greatly, successful coupling of the transducers to the environment would be difficult to consistently achieve. In order to accommodate these environmental changes, sophisticated calibration methods of guaranteeing continued accuracy would have to be employed, thus increasing the cost and complexity of the system and sending the system beyond the reach of the resources of average schools and athletic departments. Consequently, the use of ultrasonics in ball locator systems has heretofore been limited.
Because of the limitations of sound waves as just discussed, it has been known to use radio frequency systems as gaming ball locators. Since radio frequency waves travel at very high speeds, environmental conditions have little effect on the wave propagation. One prior art football locating system using radio frequency waves is disclosed in U.S. Pat. No. 4,675,816 issued to Brandon, et al. That patent discloses a ball locator system in which a gaming official positions a radio transmitter at the football's location and then energizes the transmitter to send a radio signal to a series of rotating antennas positioned at predetermined locations relative to the playing field. The antennas "home" in on the transmitted signal and through the use of triangulation principles, the position of the football is determined relative to the playing field.
The above described radio frequency ball locator, as well as other radio frequency ball locators, suffer from a number of limitations and drawbacks. Because of the relatively small area of the playing field in comparison to the speed of the signal, the accuracy obtainable by the system would be limited due to the effective beam width of the radio frequency signal. In other words, because a greater portion of the beam width would be of a sufficient magnitude for the antennas to home in on, a certain degree of unacceptable tolerance would induce sufficient errors in the calculations. Additionally, because the antennas are rotating, the radiation source must be on for a sufficient time to allow the antennas to be positioned in the desirable orientation. This places a fairly high demand on the antenna positioning system.
What is needed then is an object locating system which can be used for locating a gaming ball and which in one application utilizes the slow speed of sound waves, but does not suffer the environmental drawbacks associated with the prior art devices, or in an alternate application utilizes radio frequency technology in an effective manner. It is therefore an object of the present invention to provide these systems.